Conventional production of fuels and lubricants is still dominated by conversion of mineral petroleum feeds into desired products. In order to supplement and/or replace the conventional sources with renewable forms of energy, a variety of problems must be overcome.
One alternative to conventional fuels and lubricants is to produce comparable fuels and lubricants based on biomass. One advantage of biomass based fuels is that the resulting fuel product may be compatible with existing infrastructure and technologies. Ideally, biomass based fuels and lubricants could be used in a “drop-in” fashion in place of conventional products, allowing the use of a renewable product without having to modify existing equipment.
One option for processing of a biomass type feed is hydrothermal processing. Hydrothermal processing involves exposing a feed to water under elevated temperature and pressure conditions. U.S. Pat. No. 6,180,845 provides an example of this type of process. U.S. Pat. No. 6,180,845 describes a process for transforming biomass to hydrocarbon mixtures using near-critical or supercritical water. The process can be used on a variety of initial biomass materials. The biomass is processed at pressures from 200 bars (20 MPa) to 500 bars (50 MPa) and at temperatures from 320° C. to 500° C. The atmosphere in the reactor is described as non-oxidizing, and hydrogen is included in an example. About 4 hours is noted as a preferred processing time. The hydrothermal processing is described as producing a “petroleum like liquid”, which appears to include a substantial portion of aromatic and polymeric species, as well as some soot and/or carbonized residues. The description mentions that some metals present in the biomass feed, such as Ni or Fe, can alter the types of products generated. The description also mentions that metals can be used to simplify the components of the product mixture, or to remove unwanted compounds. The only metal specifically mentioned as an additive is Cu metal for removal of sulfur compounds such as thiophenes. Nitrogen compounds are identified as another product that can be removed by precipitation with metals, although no examples of a suitable metal are provided. It appears from the description that the additive metals used are “reduced metals”, as opposed to metals in an oxidized state.
PCT Publication No. WO 96/30464 provides another example of processing of biomass at supercritical conditions. The application describes processing of wet biomass, such as algae or water hyacinth, to produce gaseous hydrocarbons and hydrogen. The conversion conditions include contacting the biomass with water under supercritical conditions, which is defined as having a temperature of greater than 374° C. and a temperature greater than 22.1 MPa. The conversion takes place in the presence of a carbon based catalyst, such as charcoal or an activated carbon with a high surface area. The process is described as providing rapid and virtually complete gasification of organic matter in a feedstock.